In close succession both her husband and King David died, in 1152 and 1153 respectively. Following the death of Henry, who was buried at Kelso Abbey, King David arranged for his grandson to succeed him, and at Scone on 27 May 1153, the twelve-year-old was declared Malcolm IV, King of Scots. Following his coronation, Malcolm installed his brother William as Earl of Northumbria (although this county was "restored" to King Henry II of England by Malcolm in 1157[3]), and the young dowager-Countess retired to her lands at Haddington.

On Thursday 9 December 1165[4] King Malcolm died at the age of 24 without issue. His mother had at that time been attempting to arrange a marriage between him and Constance, daughter of Conan III, Duke of Brittany, but Malcolm died before the wedding could be celebrated.[5]

Following his brother's death Ada's younger son William became King of Scots at the age of twenty three. William the Lion was to become the longest serving King of Scots until the Union of the Crowns in 1603.

Religious houses were established in Haddington at an early date. They came to include the Blackfriars (who came into Scotland in 1219) and most notably the Church of the Greyfriars, or Minorites (came into Scotland in the reign of Alexander II), which would become famous as "Lucerna Laudoniae"- The Lamp of Lothian, the toft of land upon which it stands being granted by King David I of Scotland to the Prior of St. Andrews (to whom the patronage of the church of Haddington belonged). David I also granted to the monks of Dunfermline "unam mansuram" in Haddington, as well as to the monks of Haddington a full toft "in burgo meo de Hadintun, free of all custom and service."[6]

Ada devoted her time to good works, improving the lot of the Church at Haddington, where she resided. Countess Ada gave lands to the south and west of the River Tyne near to the only crossing of the river for miles, to found a convent of Cistercian Nuns ("white nuns"[7]) dedicated to St. Mary, in what was to become the separate Burgh of Nungate, the extant remains are still to be seen in the ruined parish church of St. Martin. The nunnery she endowed with the lands of Begbie, at Garvald and Keith Marischal amongst other temporal lands. Miller, however, states that she only "founded and richly endowed a nunnery at the Abbey of Haddington" and that "Haddington, as demesne of the Crown, reverted to her son William the Lion upon her death".[2]

According to inscriptions within the town of Haddington, Countess Ada's residence was located near the present day County buildings and Sheriff Court. Countess Ada died in 1178[8] and is thought to be buried locally. Her remaining dower-lands were brought back into the Royal desmesne and William the Lion's wife, Ermengarde de Beaumont, is said to have taken to her bed in Countess Ada's house to bear the future Alexander II. Miller states that when the future King was born in Haddington in 1198 it took place "in the palace of Haddington".[9]

^Roberts, John L., Lost Kingdoms: Celtic Scotland in the Middle Ages, (Edinburgh, 1997), pp. 53–54: (author states, “Almost nothing is known of him [Gille Críst, ‘Earl of Angus’] except that he married Marjorie of Huntingdon, the daughter of Henry, Earl of Huntingdon and Ada de Warenne, and that he was succeeded by his son Donnchad before 1206. His daughter Bethóc (Beatrix) was married to Walter Stewart, 3rd High Steward of Scotland and was mother to Alexander Stewart, 4th High Steward of Scotland.”).